The present invention primarily relates to a method for making a so-called knife-edge die for stamping out a pattern such as in the preparation of an electronic circuit board having pattern-wise electroconductive circuits of a metal foil bonded on the surface of an insulating base board. Such circuit boards with patterned circuits are manufactured in various ways but it is one of efficient ways to stamp out the pattern on the base board with a knife-edge die.
The knife-edge die generally has a configuration that an upstanding knife edge is provided on a die block in a closed curve line making a die element corresponding to the contour line of each of the patterns to be stamped out. The inside area on the die face surrounded by the knife-edge line of the die element and the outside area surrounding the die element are both recessed relative to the sharpened knife edge, usually, in a depth of up to a few tenths of millimeter.
These knife-edge dies for stamping out are made usually by the techniques of etching using a photoresist film provided on a die block of low carbon steel or other suitable hard material in a form corresponding to the desired pattern. The making process of such a die is therefore very complicated with repetition of etching and a high degree of skillfulness is required for the workers so that unavoidable difficulties are encountered when a shorter time for making them and lower costs are desired.
Various attempts have been made for improving the die making process utilizing the techniques of etching but none of them are satisfactory in one or other aspects (see, for example, U.S. Pat. Nos. 3,741,764 and 3,758,350).